Methane is usually distributed by being pumped through pressurized pipelines or shipped (as a solid) in refrigerated tankers. (At very low temperatures, natural gas becomes a solid,}

Geological Exploration for Oil and Natural Gas

Exploration is continually under way in search of new oil and natural gas deposits, which are usually found together under one or more layers of rock. Usually oil and natural gas deposits are discovered indirectly by the detection of structural traps, geological structures that tend to trap any oil or natural gas that is present (recall that oil and natural gas tend to migrate upward until they reach an impermeable rock layer). Two examples of structural traps ate anticlines and salt domes.

    An anticline is an upward folding of strata (rock layers). Sometimes the strata that arch up­ward include both porous and impermeable rock. If impermeable layers overlie porous layers, it is possi­ble that any oil or natural gas present will work its way up through the porous rock to accumulate under the impermeable layer.

    A number of important oil and natural gas deposits (for example, oil deposits known to exist in the Gulf of Mexico) have been found in association with salt domes, underground columns of salt. Salt domes develop when extensive salt deposits form at the Earth's surface as a result of the evaporation of

water. All surface water contains dissolved salts. The salts dissolved in ocean waters are so concen­trated that they can be tasted, but even fresh water contains some dissolved material.

    If a body of water Sacks a passage to the ocean, as an inland lake often does, the salt concentration in the water gradually increases. If such a lake were to dry up, a massive salt deposit called an evaporite deposit would remain. Evaporite deposits may eventually be covered by layers of sediment, which convert to sedimentary rock after millions of years. Because salt is less dense than rock, the rock layers settle, and the salt deposit tends to rise in a column—a salt dome. The ascending salt dome, together with the rock layers that buckle over it, provides a trap for oil or natural gas.

    Geologists use a variety of techniques to iden­tify structural traps that might contain oil or natu­ral gas. One method is to drill test holes in the Earth's surface and obtain rock samples. Another method is to produce an explosion at the surface and measure the echoes of sound waves that bounce off rock layers under the surface. These data can he interpreted to determine whether or not structural traps are present. It should be empha­sized, however, that many structural traps do not contain oil or natural gas.

    Searching for oil and natural gas is very expen­sive. It costs millions of dollars just to do the basic geological analyses to find structural traps. And once oil or natural gas has been located, drilling and operating the wells cost additional millions.

Declining Reserves of Oil and Natural Gas

Although oil and natural gas deposits exist on every continent, their distribution is uneven, and dis­proportionate shares of total oil deposits are clus­tered relatively close to each other. Enormous oil fields containing more than half of the world's total estimated reserves are situated in the politically unstable Middle East. In addition, major oil fields arc known to exist in the North Sea, the Gulf of Mexico, and the Arctic (in Alaska and Russia). Because North America has more de­posits of natural gas than Europe and other devel­oped areas, use of natural gas is much higher in North America.

    It is unlikely that major new oil fields will he discovered in the continental United States, which has been explored for oil more extensively than any other country on Earth. In the last two decades, the success rate of searches for oil has declined, as has the amount of exploration.

    There is reason to believe that large oil deposits exist on the continental shelves, the relatively flat underwater areas that surround continents. Despite a number of problems, such as storms at sea and the potential for major oil spills, many countries engage in offshore drilling for this oil. Environmentalists generally oppose opening the outer continental shelves for oil and natural gas exploration because of the threat a major oil spill would pose to marine and coastal environments. Coastal industries, in­cluding fishing and tourism, also oppose oil and natural gas exploration in these areas.

How Long Will Oil and Natural Gas Supplies Last

A major problem associated with oil and natural gas is their limited supplies. It is difficult to say with certainty how long it will be before the world runs out of oil and natural gas, because there are so many unknowns. We do not know how many addi­tional oil and natural gas reserves will be discov­ered, nor do we know if or when technological

Breakthroughs will allow us to extract more fuel from each deposit. The answer to how long these fuels will last also depends on whether worldwide consumption of oil and natural gas increases, re­mains the same, or decreases. Economic factors in­fluence oil and natural gas consumption; as reserves are exhausted, prices will increase, which can drive down consumption and stimulate greater energy efficiency and the search for additional deposits and alternative energy sources.

    Estimates on when we will run out of oil and natural gas vary from several decades to 100 years, but they are only guesses. The only thing we can say with certainty is that, at projected rates of con­sumption, oil and natural gas reserves will be de­pleted before coal.

Global Oil Demand and Supply

One difficult aspect of oil consumption is that the world's major oil producers are not its consumers. In 1989 almost half of the world's oil was consumed by North America and Western Europe, yet these same countries pro­duced only 23 percent of the world's oil. In con­trast, the countries in the Persian Gulf region con­sumed 4.5 percent and produced 26 percent of the world's oil. In the United States, a severe economic burden has resulted from the large amount of oil that is imported; more than half of our huge trade deficit in 1990 was from imported oil.

    The imbalance between oil consumers and oil producers will probably worsen in the years to come, because the Persian Gulf region has much higher proven reserves than other countries. For example, at current rates of production, North America's oil reserves would run out in ten years and Western Europe's known re­serves would be depleted in 13 years. But the Persian Gulf nations, which have 65 percent of the known world oil reserves, can produce oil at current rates for more than a century.

Environmental Problems Associated with Oil and Natural Gas

Two sets of environmental problems are associated with the use of oil and natural gas: the problems that result from burning the fuels (combustion) and the problems involved in obtaining them in order to bum them (production and transport). We have already mentioned the CO₂ emissions that are a direct result of the combustion of fossil fuels. As with coal, the burning of oil and natural gas pro­duces CO₂ that accumulates in the atmosphere, preventing the Earth's hear from radiating into

space. The Earth's climate is calculated to he warm­ing more rapidly now than it did during any of the warming periods following the ice ages. The envi­ronmental impact of rapid global climate change could he catastrophic.

    Another negative environmental impact of burning oil is acid precipitation. Although oil doesn't produce appreciable amounts of sulfur ox­ides, it does produce nitrogen oxides, mainly through gasoline combustion in automobiles, which contributes approximately half the nitrogen oxides released into the atmosphere. (Coal com­bustion is responsible for the other half.) Nitrogen oxides contribute to acid precipitation. The burning of natural gas, on the other hand, doesn't pol­lute the atmosphere as much as the burning of oil; natural gas is the cleanest of the fossil fuels.

    One of the concerns in oil and natural gas pro­duction is the environmental damage that may occur during their transport, which is often over long distances by pipelines or by ocean tankers. A serious spill along the route creates an environmen­tal crisis, particularly in aquatic ecosystems, where the oil slick can travel.

    One of the most serious oil spills ever in North America took place in Prince William Sound, off the southern coast of Alaska near the town of Valdez, on March 24, 1989. Valdez is at the south end of the oil pipeline that runs through Alaska's inte­rior from Prudhoe Bay in the north. When the su­pertanker Exxon Valdez ran aground, it dumped approximately 11 million gallons of oil into the pristine waters of Prince William Sound. An intensive cleanup campaign was mounted to remove oil from the water, rescue wildlife, protect fish hatch­eries, clean the shoreline, and assist local commu­nities that were economically hurt by the accident. The long-term environmental

Consequences of this devastating accident will take years to assess (see Focus On: Alaska's Oil Spill). The most massive oil spill in history occurred in 1991, during the Persian Gulf War, when about 250 million gallons of crude oil—more than 20 times the amount of the Exxon Valdez spill— were deliberately dumped into the Persian Gulf. Ninny oil wells were also set on fire, and lakes of oil spilled into the desert around the burning oil wells. Cleanup efforts along the coastline and in the desert were initially hampered by the war, and environmentalists fear that it may take a century or more for the area to completely recover.

To Drill or Not To Drill: A Case Study of the Arctic National Wildlife Refuge

In order to understand the complexities of energy issues, let's look at a recent controversy that has pitted environmentalists against oil developers, politicians against politicians, and Americans against Americans: the proposed opening of the Arctic National Wildlife Refuge to oil exploration. On one side are those who seek to protect rare and fragile natural environments; on the other side are those whose higher priority is the development of the last domestic oil supplies.

Background of the Arctic National Wildlife Refuge

In I960 Congress declared a section of northeast­ern Alaska protected because of its distinctive wild­life. In 1980 Congress expanded this wilderness area to form the Arctic National Wildlife Refuge— 7.3 million hectares (18 million acres) of un­touched northern forests, tundra wetlands, and gla­ciers. The Department of the Inte­rior was given permission to conduct a study of the potential for oil discoveries in the area, but explo­ration and development could proceed only with congressional approval.

    The refuge is home to an extremely diverse fish and wildlife community, including polar bears,

arctic foxes, peregrine falcons, musk-oxen, Dall sheep, wolverines, and snow geese. It also contains the calving area for a large migrating herd of caribou. The Porcupine caribou herd, named after the Porcupine River in Canada where the herd winters, contains more than 150,000 head- Dominant plants in this coastal plain of tundra include mosses, lichens, sedges, grasses, dwarf shrub*, and small herbs. Under a thin upper layer of soil is the permafrost layer, which contains perma­nently frozen water.

    Although it is biologically rich, the tundra is an extremely fragile ecosystem, in part because of its harsh climate. The organisms living here are adapted to their environment, but they live "on the edge." Any additional stress has the potential to harm or even kill them. Thus, arctic organisms are particularly vulnerable to human activities.

Support for Oil Exploration in the Refuge

Sup­porters cite economic considerations as the main reason for searching for oil in the refuge. They point out that the United States is spending a large proportion of its energy budget to purchase foreign oil. Development of domestic oil would help to improve the balance of trade and make us less de­pendent on foreign countries for our oil.

    The oil companies are eager to develop this particular site because it is near Prudhoe Bay, where large oil deposits are already being tapped. Prudhoe Bay has a sprawling industrial complex to support oil production, including roads, pipelines, gravel pads, and storage tanks. The Prudhoe Bay oil deposits have peaked in produc­tion and will decline in productivity over the next few years. As a result, the oil industry is looking for sites that can make use of the infrastructure already in place.

    The study conducted by the Department of the Interior on the possibility of oil in the wildlife ref­uge was made public in 1987. It concluded that there is a 19 percent chance of finding oil there, which the oil industry considers enough to justify exploration.

    Supporters of oil exploration argue that it will have little lasting impact on the environment or on

wildlife. They, say that there has been little envi­ronmental disruption or contamination of Prudhoe Bay by the oil industry; further, they point out that the number of caribou in that area has actually in­creased.

Opposition to Oil Exploration in the Refuge

Conservationists think that oil exploration poses per­manent threats to the delicate balance of nature in die Alaskan wilderness, in exchange for a very tem­porary oil supply. They think that the money that would be spent searching for oil would be better used for research into alternative, renewable energy sources and energy conservation—a more perma­nent solution to the energy problem. They further argue that "Drain America first" policies will only-increase our future dependence on foreign oil sup­plies.

    Opponents of oil exploration also refute sup­porters' claims that Prudhoe Bay has been devel­oped with little environmental damage. Studies such as one conducted by the U.S. Fish and Wild-

Lift Service document considerable habitat damage and declining numbers of wolves and bears in the Prudhoe Bay area; it appears to biologists that the increase in the caribou herd has been the direct result of fewer predators. The oil industry and conservationists do agree on one point: it is not finan­cially practical to restore developed areas in the Arctic to their natural states. Thus, development in the Arctic causes permanent changes in the natural environment.